1. Field of the Invention
The present invention relates generally to robotic manipulators for picking and placing objects. More particularly, the present invention relates to robotic manipulators for picking and placing data storage media in an automated storage library.
2. Discussion of the Related Art
An automated storage library is a memory subsystem of a larger data processing system. When data is required by the data processing system, a robot in the library is instructed to retrieve a data storage medium from a storage cell and load it into a read/write transfer device so that it may then be accessed by the data processing system.
Known robots retrieve data storage media, which are usually enclosed within a cartridge, by means of a two-fingered gripper arrangement. It is necessary that such robots retrieve and load data cartridges accurately and speedily since any errors or delays may lead to unwanted delays in the associated data processing system. Delays may be caused by the time taken to align the grippers with a data cartridge or by a data cartridge becoming stuck between the grippers when it is being placed in a read/write device or placed back in a storage cell.
The gripper arrangement disclosed in U.S. Pat. No. 5,015,139 includes a U-shaped ejector disposed between the gripper fingers. The ejector springs forward when a data cartridge is released from the grippers pushing the cartridge out from between the gripper fingers to prevent the cartridge from becoming stuck on the grippers.
In many data transfer devices, an example being the IBM 3480 Magnetic Tape Subsystem produced by International Business Machines Corporation, the data cartridge is inserted in a horizontal input slot and must then be pushed down into the operative position. The pushing down of the data cartridge is an additional step which must be performed by the robot in an automated storage library. In the system of U.S. Pat. No. 5,015,139 this additional step is performed by a push rod. However, there is an undesirable time delay caused by aligning this push rod in position with regard to the data cartridge and then pushing the cartridge downwards.